There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

An overview of the self-organizing map algorithm, on which the papers in this issue are based, is presented in this article.

The Self-Organizing Map

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

/pdf/a-review-of-single-phase-improved-power-quality-ac-dc-2pm6h4zjxq.pdf

A review of single-phase improved power quality AC-DC converters

Shunt Active Power Filters (SAPF) are proposed for Power Quality (PQ) improvement in perturbed power distribution networks. Conventionally, the 2-level Voltage Source Inverter (VSI) topology is used in three-phase four wire power distribution networks to mitigate current harmonics and to enhance Power Factor (PF). The Multilevel Inverter (MI) such as the Flying-Capacitor (FLC) topology is competitive with the conventionally inverters for the same targets on low voltage domain, in addition to its performance in medium voltage. In this work a comparative study of two SAPF topologies is proposed. We compare the performance for the two structures for the same modulation, same current and voltage regulation method, same control strategy using modified formulation of the p-q strategy. Firstly, it is demonstrated that the neutral current can be reduced in the conventionally 2-level structure by using a Phase Shift PWM (PSPWM) modulation instead of Sinusoidal PWM (SPWM) modulation. Secondly, peaks of source currents are reduced in the transient state by action on the Pass Band of the DC voltage regulator. Thirdly, comparison between the sizes of the inductance of the filters is made, voltage stresses on the electronic components are compared and harmonic generated by the output voltages of VSI are compared. It is demonstrated the superiority of the FLC over the two-level topology.

/pdf/a-comparative-study-between-a-conventional-two-level-and-a-3krq6v9q8a.pdf

A Comparative Study between a Conventional Two-Level and a Flying Capacitor Four-level VSI for Use in Four-Wire Shunt APF Applications

In this paper, two control laws based respectively on hysteresis and pulse-width-modulation techniques are applied on a unity-power-factor current-injection- based three-phase rectifier. A theoretical analysis is carried out in order to evaluate the performance of each technique in terms of the line current ripple and the switching frequency. The control-detuning problem, which contributes mainly to the line current distortion, is also considered. In order to highlight the comparative study, a numerical simulation is carried out.

Comparative evaluation of control laws based on pulse-width modulation and on hysteresis: application on a current-injection-based three-phase rectifier

Power loss model and efficiency analysis of grid-connected seven-switch boost-type photovoltaic current source inverter using two power switches configurations

In this research, an assemblage of pulse width modulation categories is used to control the dual stages of the indirect matrix converter. The novel modulation technique is facilely comprehended and simply put into real-time practice. An experimental prototype of the indirect matrix converter is developed. The modulation algorithm is implemented on a digital signal processor. After establishing the duty ratios and the modulation signals, the gate drive signals are formed and sent to the semiconductor devices. Keen analysis of the overall system and the overall consolidation of topology, modulation, and drive implementation is presented.

Gate Drive Implementation of an Indirect Matrix Converter with Hybrid PWM Modulation

In recent decades, the microgrid concept emerged as a solution to electrify remote areas and integrate renewable energy sources to mitigate environmental pollution. Owing to the evolution of power electronic devices, the ease of control, and the improved efficiency and reliability, DC microgrids are gaining increased interest. Many kinds of research address the hierarchical control in DC microgrids to accomplish multi-objectives. On the first and second levels, the control targets fast dynamic variables to achieve its objectives. Yet, on a third control level, general management functionalities are executed. Many of these management functionalities target the system variables with a slower dynamic and so, to prove the effectiveness of the proposed hierarchical control, a 24-hour model simulation is required. The wide time-range dynamics of the existing system variables make the 24-hour modeling subject a complicated matter especially, on standard computers with conventional performances. To overcome this problem, this paper proposes a 24-hour DC microgrid model which offers the best tradeoff between model precision, complexity, and simulation speed. The multi-objectives hierarchical control is adopted: on a first and second control level, several averaging techniques are introduced and compared to a detailed reference model in terms of accuracy and calculation step size. DC microgrid's general management strategy is adopted on the third control level. Simulation tests are performed on MATLAB/Simulink software to prove the viability of the proposed 24-hour model.

Hadi Y. Kanaan

Papers

A Comparative Study between a Conventional Two-Level and a Flying Capacitor Four-level VSI for Use in Four-Wire Shunt APF Applications

Comparative evaluation of control laws based on pulse-width modulation and on hysteresis: application on a current-injection-based three-phase rectifier

Power loss model and efficiency analysis of grid-connected seven-switch boost-type photovoltaic current source inverter using two power switches configurations

Gate Drive Implementation of an Indirect Matrix Converter with Hybrid PWM Modulation

Control and Power Management of a 24-Hour DC Microgrid Improved Model